When operating an outdoor power equipment unit such as a riding lawn mower, the operator frequently needs to dismount the unit. Most units of this type have parking brake systems to prevent the unit from rolling away when the operator dismounts. A manually operated brake lever is usually provided to engage and disengage the parking brake system. If the operator forgets to set or engage the parking brake system as the operator dismounts, the unit can roll away if the unit is located on an incline when the operator dismounts. This is obviously undesirable.
Various riding lawn mowers are controlled by twin control sticks or handles that are selectively manipulated by the operator to propel and steer the unit. The control sticks have a neutral position in which the unit is at rest. To propel the unit forwardly, the sticks are pushed forwardly by the operator from the neutral position. To propel the unit rearwardly, the sticks are pulled rearwardly by the operator from the neutral position. Steering is accomplished by pushing or pulling on one stick more than the other or even by pushing one stick forwardly while pulling the other stick rearwardly. U.S. Pat. No. 3,702,051 to Deines shows a mower of this type.
The twin control sticks of units of this type have an inboard position in front of the operator's seat where they are conveniently located in front of the operator's hands. Such control sticks are also pivotal about longitudinal, fore-and-aft axes to allow the sticks to be pivoted laterally into outboard positions. In their outboard positions, the control sticks have been laterally moved to positions that are further to the sides of the operator's seat.
U.S. Pat. No. 6,434,917 to Bartel shows a twin stick mower in which the control sticks are linked by mechanical linkages to a parking brake system comprising a pair of parking brakes, one for each drive train controlled by each control stick. When the operator pivots the control sticks into their outboard positions, the mechanical linkages automatically engage the parking brakes. However, in Bartel, the mechanical linkages are elongated and extend vertically to connect between the parking brakes and the control sticks. Moreover, the linkages include ball joints to accommodate the lateral pivoting of the control sticks when the control sticks are placed in their outboard positions. Thus, the mechanical linkages are relatively cumbersome and are located in an area of the mower where space is tight.
U.S. Pat. No. 6,739,116 to Stover discloses an alternative to Bartel in which an electrical solenoid is used as an actuator for the parking brakes. When the control sticks are in their inboard positions, this is sensed by an electrical switch which acts to energize the solenoid to cause the parking brakes to be disengaged. When the control sticks are pivoted outwardly by the operator into their outboard positions, this is also sensed through the switch and the solenoid is deenergized, allowing a biasing spring to then move the parking brakes into an engaged position. However, while this system is effective, the use of an electrical solenoid is relatively costly and the force provided by a solenoid is not constant over its entire stroke.